Effect of size and base-element on the jerky flow dynamics in metallic glass

The jerky flow behavior of metallic glasses (MGs) is systematically investigated in this work for various alloy compositions, ranging from the commonly conceived ductile MGs, such as those based on Zr and Cu, to the brittle ones, such as those based on Mg and Fe, on the microscopic scale. Through extensive microcompression studies, a clear sample size and base-element dependence of the jerky flow in MGs is revealed, which shows that the stress-drop amplitude, as normalized by the corresponding MG yield strength, reduces with decreasing sample size or increasing elastic modulus. Meanwhile, the temporal discontinuity of the jerky flow, as characterized by the duration of the stress-drop event and the delay between two consecutive events, also displays similar size and base-element dependence. Finally, a unified theory based on stick slip dynamics is proposed to explain the coupled size and base-element effects. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.